bytewired/mova-poc

Description

Mova is a stack-based VM with abilities to save, restore and transmit its own state to continuous execution from interrupted point.

Components

• OpCodes dictionary
• Compiler
• Virtual Machine
• Serializator/Deserializator (Marhalling/Unmarshaling?)
• Hypervisor

OpCodes dictionary

Instruction	HEX	Description
PUT	0x01	Puts value onto stack
ADD	0x02	Sums value with the latest onto stack and put result onto stack
GOTO	0x03	offset is an instruction offset; goes to instruction backwards onto the offset
PRINT	0x04	Prints the latest value onto stack
SLEEP	0x05	Sleeps for value in milliseconds

Test code

Mova bytecode representation:

PUT 0
ADD 1
PRINT
SLEEP 100
GOTO <ADD offset, in this case it's 3>

Pseudo language representation:

var i = 0;
loop: 
    i++;
    print(i);
    sleep(100);

VM Structure

Component	Description
Hypervisor Listener	Listents to incomming commands from Hypervisor
VM	Program executor
State Serializator	Serializes/Deserializes program state (Instruction Pointer, Stack)

Hypervisor Listener

Each program is a socket server and Hypervisor is a client that binds to server(s).

Hypervisor component into VM listens to incomming clients.

Socket port for server is calculated based on this [PID]^34567.

Supported commands:

Command	Description
save
restore

State Serializator

Stack Segment Structure

Value	Description
0x3ACC	segment header
16 bit usigned int	stack size
32 bit usigned int	stack element size

The first item in the segment is the bottom item in stack.

Instruction Pointer Segment Structure

Value	Description
0x101E	segment header
32 bit usigned int	defines IP value

Data Segment Structure

Assume that both VMs runs the same version of the same program.

Hypervisor Structure

Component	Description
IPC component	Component to communicate between two processes
CLI executor	Commands executor

Hypervisor commands

Command	Description
ps	get list of processes that runs Mova VM
bind <PID>	bind to program's socket
unbind <PID>	unbind from program's socket
rstate <PID>	read state from program
wstate <PID from> <PID to>	take state from one program that was fetched by rstate and send to another program